Production of lubricating oils from aromatic extracts



June 14, 1966 R. H. KozLowsKl ETAL 3,256,175

PRODUCTION OF LUBRICATING OILS FROM AROMATIC EXTRACTS Filed Oct. 23,1964 z BY i?" Z657;

TORNEYS United States Patent PRODUCTION 0F LUBRICATING OILS FROMAROMATIC EXTRACTS Robert H. Kozlowski, Berkeley, and Robert L. Jacobson,

Pmole, Calif., assignors to Chevron Research Company, a corporation ofDelaware Filed Oct. 23, 1964, Ser. No. 406,138 4 Claims. (Cl. 208-58)This application is a continuation-in-part of our copgriging applicationSerial No. 163,923, filed January 2,

This invention relates to the production of lubricating oils andlubricating oil base stocks by catalytic hydrogenati-on. In particular,the invention relates to the production of improved lubricating oils bya combination of solvent treating and catalytic hydrogenation.

In the conventional production of lubricating oils by petroleum rening,crude oil segregated on the basis of its high content of desirable lubeconstituents is distilled to obtain fractions boiling in the lubricatingoil range, each of said fractions representing a source of lubricatingoil of a separate viscosity range. The said fractions are thenseparately s-olvent treated, usually with solvents for aromatics such asSO2, phenol, furfural, and the like, to obtain lubricating oilraflinates often referred to as neutral distillates, and aromaticextracts. The severity of the solvent treating of each fraction in termsof solvent dosage or solvent t-o oil ratio is controlled to produce araffinate having the viscosity `desired in the particular lubricatingoil product and to sufficiently improve the color and stability suchthat salable lubricating oil can be recovered directly or produced byfurther simple treatment such as dewaxing, acid treating, and/ or claycontacting.

The aromatic extracts so produced contain a high percentage of thematerials causing oils to have poor color, instability, and lowviscosity index, and hence they are recognized as having no valueinsofar as lubricating oil production is concerned. Accordingly, theextracts are disposed of by blending into low grade fuel oil or intothermal cracker or cat cracker feed.

By means of the present invention an increased yield of high qualitylubricating oil can be obtained from the crude oil by converting sucharomatic extracts into recoverable lubricating oil by severe catalytichydrogenation. In accordance with the invention a crude oil is distilledto obtained fractions boiling in the lubricating oil range, including alight fraction and a heavy fraction representing sources for lubricatingoils of separate viscosity ranges, and the said fractions are separatelysolvent treated to obtain respectively a light lube rainate and a lightaromatic extract and a heavy lube rainate and a heavy aromatic extract.At least a portion of the heavy aromatic extract is hydrogenated bycontacting with a sulfactive hydrogenation catalyst and hydrogen atsevere conditions of elevated temperature, high pressure, and low spacevelocity whereby a substantial portion thereof is converted todistillate fuels, From the products of the severe hydrogenating thereare separated distillate fuels and a hydrogenated oil having a viscosityin the range of the light lube raffinate, and at least a portion of thehydrogenated oil is combined with the light raffinate. The combinedlight raffinate and hydrogenated oil, and the heavy rainate, can then befurther separately treated if desired or necessary, to obtain improvedquality lubricating oils in separate viscosity ranges.

3,256,175 Patented June 14, 1966 The attached drawing, to which moredetailed reference will be made hereinafter, illustratesdiagrammatically a flow scheme for carrying out the invention andcertain alternates in the manner of combining the hydrogenated oilrecovered from severe hydrogenation of the extract with the lightrailinate.

Reference herein to materials boiling in the lubricating oil range isintended to include the boiling range of all materials conventionallyrecovered as lubricating oil. It is recognized that lubricating oils arerarely specied on the basis of boiling range, other than to specify aflash point, the primary criterion being always viscosity to definedifferent lubricating oil grades. Thus, depending on the properties ofthe initial crude oil, the boiling range of a particular viscosity rangelube oil may vary within substantial limits. Generally, however,lubricating oils boil essentially entirely above about 550 F.

The term raffinate is used herein in its broadest sense as referring toa solvent relined oil recognized as containing the desirable lubricatingoil constituents. Preferred lubricating oils are essentially naphthenicin basic structure, and have alkyl substituents of varying cornplexity.Essentially parainic or waxy hydrocarbons are not desired, nor areessentially aromatic hydrocarbons, because of their poor lubricatingproperties. Where the crude distillate is treated with a solventselective for aromatics, the reference to the lubricating oil portion asa rafliuate is technically correct since the undesired aromatichydrocarbons dissolve in the solvent as the extract phase. Nevertheless,it is conventional in the lube oil refining art to refer to thenonaromatic material obtained by solvent extraction as the raffinateeven in those cases where a solvent is used which rejects the aromaticconstituents and dissolves the desired lubricating oil material.

The manner of employing the severe catalytic hydrogenation of anaromatic extract for producing lubricating oil in the present inventionis quite different from previous methods proposed for using catalytichydrogenation in the refining of lubricating oils. While hydroiinishinghas been employed heretofore as a substitute for acid treating or claycontacting of refined lube oils or raffinates, such processes userelatively mild conditions of low temperature, low pressure, and highspace velocity so as to avoid lowering the viscosity of the raflinate.Destructive hydrogenation has also been proposed as a substitute forsolvent extraction of crude lube oils, using severe conditions of hightemperature and pressure. In such v processes, the proposal was tosubject to destructive hyand, as a result, it is possible to achievebettercontrol.

over the yield of lubricating oil in different viscosity ranges.

The catalysts heretofore employed or proposed for .usev

in the prior art lube oil hydrofining'processes were usually eitherhydroning catalysts, such as molybdenum oxide, cobalt molybdate,nickel-tunsten sulfide, etc., or hydrogenation catalysts such as nickelor platinum. Usually the catalyst metals, oxides, or suldes aresupported on a carrier such as alumina, silica-alumina, or magnesia. Theolder supported hydroning catalysts have invariably a low metal contentof less than 15% by weight. Recently, more active catalysts have beendiscovered. For example, there is disclosed in our U.S. Patent No.3,114,701 certain highly active catalysts comprising nickel sulde andmolybdenum sulde in combination with a support such as alumina, withunusually high molybdenum content of 15.5-30% and high nickel content of4-10%. The term sulfactive hydrogenation catalyst is used herein withreference to all such catalysts as are recognized as useful forhydrogenation of nitrogen and sulfur compounds in oils and for thehydrogenation of oils containing nitrogen and sulfur compounds. The termthus excludes the noble metal hydrogenation catalysts such as platinumand nickel unpromoted with a Group VI metal, which are poisoned -bysulfur and nitrogen compounds. Further, it will be appreciated thatmarkedly superior results are obtained by using'the catalysts havinghighest activity for the hydrogenation of oils containing nitrogen andsulfur compounds.

The hydrogenation of the aromatic extract suiciently to convert it tomaterial suitable for lubricating oil is a difficult job to accomplish,and accordingly requires severe conditions. In particular, the pressureemployed will be at least 2,000 p.s.i.a. hydrogen partial pressure andmay range upwards of 10,000 p.s.i.a. Generally pressures of 200G-3000p.s.i.a. are preferred. The temperature should be in the range G50-800F., extremely high temperatures being avoided in order to favorhydrogenation, and the space velocity will be in the range 0.2-1 LHSV soas to provide suicient time for the conversion without using excessivelyhigh temperatures. The hydrogen-to-oil ratio is generally between 2,000and 10,000 standard cubic feet per barrel (s.c.f./'b'bl.). Because ofthe diiculty of hydrogenating the highly aromatic and contaminated oil,there is preferably used a highly active catalyst such as the suiidedhigh metal content nickelmolybdenum catalysts. As a guide in determiningthe suitability of a particular catalyst, it should be capable ofremoving at least 95% of the nitrogen compounds contained in the extractby hydrogenation to ammonia at conditions in the aforementioned ranges.The obtaining of greater than 95 nitrogen removal is used as a guide orcriterion for determining that suiicient hydrogenation is beingaccomplished. At the conditions necessarily employed, at least a portionof the aromatic extract will be converted to distillate fuel comprisinghydrocarbons boiling in the range of gasoline, kerosene, and middledistillates lower boiling than generally included in lubricating oil.Accordingly, such distillate fuels are separated from the products ofthe hydrogenating to recover a heavier portion comprising hydrogenatedoil suitable for incorporating into lubricating oil.

The heavy hydrogenated oil can be incorporated into lubricating oil inseveral ways. The hydrogenated oil may simply ybe blended with the lightrainate obtained from the solvent treating. In another, and frequentlysuperior method, the hydrogenated oil is combined with the lightfraction prior to the solvent treating step so that a major portion ofthe hydrogenated oil is ultimately recovered in combination with thelight rainate produced in solvent treating. vThe aromatics content ofthe hydrogenated oil is sufficiently low, usually below by volume, suchthat very little of it is extracted by an aromatic solvent such asphenol, but the solvent treating advantageously improves thehydrogenated oil in other respects such as color and stability.

In other methods of operation, the combining of the hydrogenated oilwith the ranate and the treatment of other oils in the process may becarried out as illustrated in the attached drawing. Referring to thedrawing, a crude oil such as an atmospheric residuum or a vacuumdistillate in line 10 is distilled in distillation zone 11 to obtain alight fraction in line 12 and a heavy fraction in line 13 representingsources for lubricating oils of Separate viscosity ranges. In addition,there may be obtained a lighter lubricating oil fraction or a lighternonlubricating oi-l distillate -in line 14. In the case of the residualfeed there may be obtained'an asphaltic residuum in line 15. The oils inlines 12 and 13 are rich in polycyclic hydrocarbons preferably,including both naphthenic and aromatic hydrocarbons, and containnitrogen cornpounds i-n addition to other hetero organic contaminantssuch as sulfur and oxygen compounds.

The light lubricating oil fraction in line 12 is passed tosolvent-treating zone 17 wherein it is contacted with a solvent foraromatics such as phenol, furfural, and the like, in a manner wellknown. After recovery of solvent from the resulting two phases, there isrecovered in line 18 a light lubricating oil rainate and in line 19 alight aromatic extract. The heavy fraction in line 13 is similarlytreated in solvent treating zone 20 to obtain, after recovery of thesolvent, a heavy lube rafiinate in line 21 and a heavy aromatic extractin line 22. If the feed is a residual, all or part of the residue inline 15 may be passed via line 16 to zone 20, in which casea brightstock is obtained in line 21 and heavy resins in line 22.

In the embodiment illustrated, the light fraction in line 12 issolvent-treated in combination with a hydrogenated oil in line 28obtained as set forth hereinafter, using a relatively mild solventdosage to obtain a high yield of light ranate in line 18 of poor colorand higher than desired viscosity and a low yield of aromatic lightextract in line 19. The heavy fraction in line 13 is treated in zone 20using a relatively severe solvent dosage to obtain a high yield ofaromatic heavy extract in line 22 and a relatively lower yield of heavyraffinate in line 21, which is a heavy lubricating oil base stock ofgood color and desired viscosity. y

At least the heavy aromatic extract in line 22 is passed to severehydrogenation Zone 23 wherein it is thoroughly hydrogenated bycontacting with a sulfactive hydrogenation catalyst and hydrogen atsevere conditions of high temperature and pressure and low spacevelocity whereby a substantial portion thereof is converted todistillate fuels. In carrying out the catalytic hydrogenation anysuitable equipment arrangement may be used for contacting the oil withthe catalyst in the presence of excess hydrogen. For example, thecatalyst may be maintained as one or more fluidized lbeds, gravitatingbeds, or iixed beds of small particles, through which the oil andhydrogen are passed, upow or downfiow, concurrent or countercurrent. Aslurry of catalyst in oil may also be used. Usually, the catalyst is inthe form of small pellets or rod-like extrusions contained in a reactoras several fixed beds, and the oil and hydrogen are passed togetherdownow through the bed at controlled temperature, pressure, and ow rate.The effluent is cooled to separate product oil from hydrogen-rich gaswhich is recycled. The oil thus obtained is passed via line 24 todistillation zone 25 wherein the products lof hydrogenation areseparated into distillate fuels and lighter hydrocarbons in line 26 andin line 27, a hydrogenated oil having a viscosity in the range of thelight fraction. As indicated, all or a portion of the hydrogenated oilin 'line 27 is returned vi-a line 28 to the solventtreating zone 17 forextraction in admixture with the light fraction of line 12. The lightranate in line 18 will thus contain a major portion of the hydrogenatedoil so passed via line 28.

In the particular embodiment illustrated in the drawing, this rainate ispassed to hydrogenation zone 29 wherein it is hydrogenated by contactingwith a sulfactive hydrogenation catalyst and hydrogen at less severeconditions, including lower temperature and higher space velocity ascompared-to the conditions used in zone 23 in hydrogenating the aromaticextract, whereby no substantial portion of the raffinate in line 18 isconverted to light distillates. While conditions in zone 29 aresubstantially less severe than in zone 23, the conditions are moresevere with respect at least to pressure than used in simple, mildhydroning of finished lubricating oils. Thus, hydrogenation in zone 29is preferably carried out in the manner disclosed and claimed in ourprior-led copending application Serial No. 163,923, namely by employingpressures in the range 150G-3000 p.s.i.a. hydrogen partial pressure,temperature of 650-750 F., and space velocity of 0.5-3 LHSV toaccomplish a significant lowering of the viscosity with limitedconversion of nitrogen compounds to ammonia in the range 30-60%, Wherebythe color and oxidation stability of the hydrogenated oil are improved.

The hydrogenated oil obtained in line 30 is passed to distillation zone31 wherein light hydrocarbons'and any small amount of distillate fuelsproduced.may be withdrawn through line 32 and the desired lightlubricating oil base stock recovered in line 33. In one type ofoperation of the process of this invention, all or a portion of theseverely hydrogenated oil in line 27 may be diverted through line 37 andpassed via line 35 to distillation zone 31. The hydrogenated oil sopassed can be recovered in the light lubricating oil product of line 33.In this case, however, it will frequently be found desirable to withdrawa small bottoms portion in line 34 to obtain more precise adjustment ofthe nal lubricating oil viscosity.

In another embodiment illustrated in the drawing, the light aromaticextract of line 19 is also passed to severe hydrogenation zone 23 withthe heavy aromatic extract of line 22. It will then be foundadvantageous to separate the severely hydrogenated oil into a heavyportion dewaxing process.

The invention may 'be further explained and the advantageous resultsobtainable thereby be better demonstrated by means of the followingexamples. In the examples, where reference is made to a suliidednickelmolybdenum catalyst, the catalyst employed was prepared byimpregnating a high purity alumina base with nickel nitrate, calcining,then impregnating with ammonium molybdate, being calcining, againimpregnating with ammonium molybdate, and calcining. The oxide catalystso produced, which contained about 6% nickel and about 20% molybdenum,was suliided by contacting With hydrogen containing dimethyl disulfide,equivalent on hydrogenation to 2% H28, at about 500 F. to convert themetal oxides substantially to the sulfdes prior to the use in thecatalytic hydrogenation process.

EXAMPLE 1 uct, the properties of which are also given in Table I. l

Stock Gravity, APT Viscosity, SSU at 100 F Viscosity, SSU at 210 FViscosity Index ASTM- Aniline Point Aromatics, percent Pour Point, FNatural Oxidation Stability, hours Nitrogen, p.p.m Boiling Range, FPercent Nitrogen Remova1 Color,

1 Black.

2 -l-Saybolt.

in line 27 and a somewhat lighter portion in line 36. The heavy portionin line 27 will contain most of any remaining aromatic constituent inthe oil, and is accordingly returned via line 28 to solvent extractionzone 17. In many cases, however, the aromatics content will be lowenough so that re-extraction is not needed, and the heavy portion caninstead be passed via line 38 to hydrogenation zone 29 with the Ilightratlinate. The lighter portion in line 36 may be passed via line 35 fordirect recovery with the light lube fraction of line 33 in distillationzone 31.

Thus, in accordance with the illustrated embodiment of the invention,there are recovered in lines 33 and 21 light and heavy lubricating o ilsor lube oil base stocks in separate viscosity ranges, of improved colorand oxidation stability. In most cases, however, it will be desirable togive these fractions at least some further mild treatment as by claycontacting preceded by or following dewaxing to meet all specificationsdesired for` the ultimate salable lubricating oils. In addition, it willbe understood that various inhibitors and additives will be added to theproduct fractions ultimately sold. Dewax- It will be noted that the lubeoil produced by catalytic 5 lhydrogenation of the extract in accordancewith the invention was quite similar to the raflinate. In most respects,such as aromatics content, pour point, and viscosity index, thehydrogenated extract was .superior to the lube oil raffinate. Theviscosity, however, is substantially lower than that of the rainate. Ahigher yield of lube oil more closely resembling the aforementionedrainate in viscosity is obtained by catalytic hydrogenation of anextract obtained by solvent treating a heavier naphthenic lubedistillate, as in the following example.

EXAMPLE 2 are also compared with'those of the raffinate produced inpreparing the extract feed of Example 1.

ing said heavy fraction to obtain a heavy lube rainate and a heavyaromatic extract,

Table 'II Hydrogenated Extract Pro crt Extract p Y whole 16% 84% StockOverhead Bottoms Ratlnate of Example 1 Gravity, API Viscosity, SSU at100 F Viscosity, SSU at 210 F Viscosity Inder Color, ASTM Aniline PointAromatics, Percent Pour Point, F

Natural Oxidation Stability,

Boiling Range, F 723-997 352-944 37H60 Nitrogen, p.p.m 8, 000 210Percent Nitrogen Removal" 97 lBlack. 2 Clear yellow.

In the foregoing example it will be noted that a major portion of theseverely hydrogenated oil produced by treating the heavier aromaticextract of the higher viscosity fraction had a viscosity substantiallythe same as that of the rainate produced by solvent extraction of thelower viscosity fraction of Example 1. The boiling ranges of these oils,however, are not the same as the hydrogenlated oil has a higher endpoint.

The rafiinates produced by solvent extraction in the above examples wereof good quality, and would not require further hydrogenation but onlymild clay treating to finish them as product lubricating oils. Theobtaining of raiiinates of this quality, it will be recognized, dependson the severity of solvent treating in terms of the dosage or solvent tooil ratio in particular. By using in accordance with the invention arelatively severe or high solvent dosage in treating the heavierfraction, there is obtained a greater amount of aromatic extract forconversion to oil resembling the raffinate of the lighter fraction,thereby increasing the total production of lighter lubricating oil. Thisyield of lighter lubricating oil can be further increased by using larelatively mild solvent dosage in the solvent extraction of therelatively light fraction, and then hydrogenating at less severeconditions the light rainate so as to adjust its viscosity, color, andoxidation stability. Where instead, it is desired to obtain a higheryield of the heavy lube product, the conditions of solvent treating therelatively heavy raffinate can be milder, and the resulting heavyraffinate can be given a less severe hydrogenation.

lt will be recognized that the light and heavy distillate fractions andthe light and heavy lubricating oils referred to herein are notnecessarily in adjacent viscosity ranges, but may be separated by an oilof intermediate viscosity. Further, it will be understood that thesolvent treating zones referred to are not necessarily separate unitsand that the entire process is not necessarily carried out continuously.Thus, there may be but one solvent treating unit which is usedalternately to treat the light fraction and then at another time totreat the heavy fraction, the fractions derived from the distillationand the raiiinates and extracts being temporarily held in storage.Likewise, where there is employed both severe hydrogenation and a lesssevere hydrogenation the same processing equipment may in many cases beused for both treatments in blocked operation at differenttimes,intermediate storage again being required.

We claim:

1. The process which comprises distilling crude oil to obtain fractionsboiling in the lubricating oil range, including a light fraction and aheavy fraction representing sources for lubricating oils of separateviscosity ranges,

solvent treating said light fraction to obtain a light lube raffinateand a light aromatic extract, solvent treathydrogenating at least aportion of said heavy extract by contacting wit-h a sulfactivehydrogenation catalyst and hydrogen at severe conditions of hightemperature and pressure and low space velocity Whereby a substantialportion thereof is converted to distillate fuels,

separating from the products of said hydrogenating distillate fuels anda hydrogenated oil having a viscosity in the range of said lightratinate,

and combining at least a portion of said hydrogenated oil with saidlight raffinate.

2. The process of claim 1 wherein a major portion of said hydrogenatedoil is combined with said light raiiinate by combining said hydrogenatedoil with said light fraction prior to solvent treating said lightfraction.

3. The process which comprises distilling crude oil t0 obtain fractionsboiling in the lubricating oil range, including a light fraction and aheavy fraction representing sources for lubricating oils of separateviscosity ranges,

solvent treating said light fraction to obtain a light lube raffinateand a light aromatic extract, solvent treating said heavy fraction toobtain a heavy lube ratinate and a heavy aromatic extract,

combining at least a portion of said light extract with at least aportion of said heavy extract and hydrogenating the combined extracts bycontacting with 'a sulfactive hydrogenation catalyst and hydrogen atsevere conditions of high temperature and pressure and low spacevelocity whereby a substantial portion thereof is converted todistillate fuels,

separating from the products of said hydrogenating distillate fuels anda hydrogenated oil having a viscosity in the range of said lightraiiinate,

combining at least a portion of said hydrogenated oil with said lightrainate and hydrogenating the combined light raflinate and hydrogenatedoil by contacting with a sulfactive hydrogenation catalyst and hydrogenat less severe conditions including lower temperature and higher spacevelocity as compared to the conditions used in hydrogenating saidextracts, whereby no substantial portion thereof is converted to lightdistillates.

4. The process which comprises distilling crude oil to obtain fractionsboiling in the lubricating oil range,- including a light fraction and aheavy fraction representing sources forlubricating oils of separatedesired viscosity ranges;

solvent treating said light fraction in combination with a hydrogenatedoil obtained as set forth hereinbelow using a relatively mild solventdosage to obtain a high yield of light raiiinate of poor color andhigher than desired viscosity and a low yield of aromatic light extract;

solvent treating said heavy fraction using a relatively severe solventdosage to obtain a high yield of by no substantial portion thereof isconverted to aromatic heavy extract and a low yield of heavy lightdistillates;

raffinate which is a heavy lubricating oil base stock and recovering asthe principal product of said less of good color and desired viscosity;severe hydrogenating a light lubricating oil base stock v combining atleast a portion of said light extract with 5 of good color and desiredviscosity.

at least a portion of said heavy extract and hydrogenating the combinedextracts by contacting with References Cited by the EXalllllel asulfactive hydrogenation catalyst and hydrogen at UNITED STATES PATENTSsevere conditions of high temperature and pressure and low spacevelocity whereby a substantial portion 10 gamer et al 20S-264 thereof isconverted to distillate fuels erge? 20S-"254 2 905 636 9/1959 Watkins etal. 208-254 separating from the products of said severe hydrogenat-2944006 7/1960 Scott 208 89 ing distillate fuels and a hydrogenated oilhaving a 2983676 5/1961 Howlgl 208 254 viscosity in the range of saidlight rainate; 2988501 6/1961 Inwood 208 254 Combining Saidhydl'ogenated the Said 15 Tucker fraction for solvent treating asaforesaid; 3014860 12/1961 Douwes et aL 208 254 hydrogenating Said lightra'nate by Contacting with 3,046,218 7 /1962 Henke et aL 208 144 asulfactive hydrogenation catalyst and hydrogen at 3,094,480 5/1963Richardson 20g 143 less severe conditions including lower temperatureand higher space velocity as compared to the 20 DELBERT E. GANTZ,PrmaryExaminer. conditions used in hydrogenating said extract, where- S. P.JONES, Assistant Examiner.

